Oaks (genus Quercus) comprise a large, widely distributed, and diverse
group of plants. But why has Michael Steele written a book entirely dedicated to seed dispersal of a single genus? The answer is that, from the
perspective of seed dispersal, oaks are one of the most complex and interesting groups of plants in the world. Oaks are dispersed almost entirely
by the actions of nut-caching animals, primarily rodents and jays. These
animals bury nuts in shallow, widely scattered sites, and, if not reclaimed
by an animal, the acorns can germinate and produce new plants. These are
old and complicated coevolved relationships between plants and dispersers. These complexities arise from the genetic diversity of oaks (the genus has five distinct sections), the broad variety of habitats (e.g., tropical,
north temperate, and semi-arid), and the wide geographic range (North
and Central America, Europe, and Asia) over which oaks are found. In
these different environments, oaks have interacted with a wide variety of
seed-dispersing animals. Further, across this range, there is a wide variety
of seed predators (e.g., weevils, boars, and acorn woodpeckers) that act
as parasites of the mutualism. These animals and physical environments
exert strong selective pressures on seed morphology, nutritional content,
and germination behavior.